Process for making power transmission fluids



Patented Aug. 1, 1950 [UNITED STATES PATENT 1 OFFICE 2,517,044 a r e PROCESS FOR MAKING POWER" y TRANSMISSION FLUIDS a i a William Percival Smith, Leamington Spa, Eng- 5; 5;; y land, assignor to AutomotivegProducts Company Limited, Leamington Spa, England y ,WNo Drawing. Application September 5,1944; Se-

This invention relates to power transmission fluids of the type comprising castor oil and a diluentsuch as an ether or ester of glycol or glycerine.

Castor:oil is a well known ingredient of power transmission fluids owing to-its lubricating properties and the fact that 'it does not adversely affect the rubber parts of brake mechanism nor corrode the metal parts; and also the extended range of temperatures over which its viscosity has little variationfand mixtures of glycol ethers and castor oil have been popular for this purpose for anumber of years. i i ,A solution of castor oil in Cellosolve in the proportion of 35% castortoil, 65% Cellosolve whichhas been brought to practical neutrality by means of a solution of potash in Cellosolve, has been standardised andwill remain liquid down to a temperature of -40 C. t a

The exacting conditions of modern aircraft work make it necessary toproduce power transmission fluids which will remain liquid at much lower temperatures and still retain the same properties as the castor oil-Cellosolve mixtures at the normal and elevated temperature ranges.

Itjhas now beenfound that if the neutralisation step is carried out in such a way, when making a castor oil-Cellosolve ,mixturegthat before adding the :bulkof the Cellosolve asom'ewhat greater amount of caustic potash is added them that required to neutralise the free acidity of the castor oil, and at the slightly elevated temperatures' normally employed in mixingthese fluids, viz about 30 -4 0 CL, ifsufiicient time is allowedtoelapse (determined by alkalinity tests) to allowofacertainamount of saponification to take place until the neutral point is reached and thereupon the bulk of the Cellosolveis added, a solution may be produced which has a consider ably increased water tolerance and will remain liquid at temperatures as low as minus 60 C.

The 35% 65% castor oil-Cellosolve mixture is: a standard mixture and has beenfoundto meet most of the requirements of power transmission fluids, except the highly exacting low temperature conditions required for certain T purposes,

and the fact that these low temperature stand-H ardsoan'now be attained without alteringthe composition rof the fl uid, is a discovery of the first importance andfis believed to be of general application. where neutralised castor oil-glycol monoether fluids are made up.

It was believed that the saponification prod-: ucts thus formed in the castor oil were anzessen- W 1 l sa h? p ewarp anes.19w emperature fluid.

il'isal3 No. 552,820. In Great Britain July 26,

Considerable further investigation has however shown that this is not the case but that on the contrary both in the case of castor oil and in the case :of pure glyceryl tri-ricinoleate if the oil in a castor oil or tri-ricinoleate-Cellosolve fluid be recovered by repeated washing with distilled wateruntil no more soap can be extracted whereby the saponification products are eliminated from the oil, and if the oil thus -modified :is again made up into the 35% oil-Cellosolve mixture a still further increase in the water tolerance (24%) is obtained and a fluid with afreezing point as low as -'73 C. was obtained inthis way. Furthermore it was found thatlthe same result of high water tolerance and low freezing point could be obtained immediately by treating the dry Cellosolve with metallic sodium to form an alcoholate withthe remaining alcoholic hydroxyl group of the glycol ether and adding the alcoholate to a mixture of Cellosolve and glyceryl tri-ricinoleate.

The present invention is not dependent on any theory as to what takes place but possibly some reaction of the alkali metal with the glycol ether analogous to the formation of an ether from an alcohol takes place in the absence of water. However, it has been found that there is an optimumamount of alkali which can be added beyond which no further addition of alkali improves the water tolerance and freezing point figures.. This amount can be easily arrived at under any given conditions by previous trial with titration and water tolerance tests.

It has beeniound that either castor oil or pure glyceryl tri-ricinoleate may be used in carrying out the process of the present invention and the term glyceryl tri-ricinoleate will be used hereinafter to signify either commercial castor oil or the chemically prepared ester.

7 According to the present invention a process for the preparation of a fluid for transmission of power comprises essentially treating glyceryl triricinoleate in the presence of a glycol monoether with an alkali hydroxide or ralcoholate in excess of that required to neutralise the free acidity of the tri-ricinoleate.

.Conveniently, according to the invention the alkali hydroxide or the alcoholate may be prepared by dissolving thehydroxide in or reacting the alkali metal with a small proportion of the glycolmonoether to be used. Theamounts of the constituents may be chosen so that the final fluid has the composition 35% oil and monoether approximately.

The alcoholate may be produced in situ by adding metallic sodium or potassium to a tri- 65 glycol with a glycol monoether e. g. with Cellosolve to bring the proportions to 35% oil and 6.5% .Cellosolve The amount of alkali hydroxide or alcoholate which must be added to obtain optimum results varies according to the conditions obtaining'during mixing, but this can easily be determined by a previous trial accompanied witha water tolerance :test.

According to one wayof carrying :out the invention, castor oil and Cellosolvemay be mixed in the proportion of 35% castor oil and 65% Cellosolve, but conveniently only a small proportion, say of the Cellosolve is mixed with the castor oil in the first instance and the required-amount of alkali, for example potash, may be mixed with this portion of the Cellosolve before it is mixed with the castor oil, and when the Cellosolve solution of the potash is :mixed with the castor oil, the mixture may be-allowed to stand until tests show that the .solution .has lost its alkaline reaction and become neutral.

In order that the interval required for completing this reaction is :not too long, .it is desirable to raise the temperature of the ingredients somewhat, the actual temperature chosen being arrangedso that a convenient intervalfor making tests is allowed. This may be effected by storing the castor oil .in :a warm :room, say at about HP-45 C. As soon as neutrality is reached, the remainder of the Cellosolve is added so that no further reaction takes place owing to the dilution of the caustic potash.

The following examples give specific ways of carrying out the invention by way of illustration only:

Example .1

205 gallons of'castor oil '(which has been stored at a temperature of 45 C.) was pumped into a mixer and mixed with 122 gallons of Cellosdlve in the following manner:

The castor oil contained in 5 drums was pumped into the mixer, one drum ata time, and in between each drum a similar proportion of the Cellosolve was pumped in, but before the last drum of C'ellosolve was pumped into the mixer 4 gallons of filtered solution of potash in Cellosolve, containing 35 ozs. potash per gallon of Cellosolve, was placed into the last drum and roughly mixed, and then this drum Was pumped on to the top of the contents in the mixer, it being arranged so that the Cellosolve containing the potash is pumped in on the top o'f the layer of Cellosolve, so that there .is no appreciable contact of castor oil and potash solution until all is ready for the mixing. Mixing was then commenced until a, homogeneous solution was obtained and a sample was drawn out for testing (the temperature being found to be 30 C.) and was found to have a, water tolerance (measured by adding water to 100 cc.1sample) of 19; and alkalinity test was made by titratingJ20 4 ccs. of the fluid with N/ HCl using phenol phthalein as indicator. This first test showed that 0.8 cc. of acid was required before neutrality was reached. After standing five minutes and agitating for minutes, similar tests showed water tolerance .20 alkalinity 0.2 cc. The fluid was then allowed to stand without agitation for a further 20 minutes when it gave water tolerance 21 and alkalinity 0.01 cc. At this point a.

further 258 gallons of Cellosolve were pumped into the mixture and tests showed water tolerance 20.7, alkalinity :faintly on the acid side of neutral, viscosity 38 seconds at 38 C. equivalent to 5.36 centisto'kes.

Ezvample 2 4000 cc. of fluid was made up using 35% chemically prepared glyceryl tri-ricinoleate, 65% Cellosolve. After 6.25 gms. of KOH (0.23 oz./gal.) had been added and mixed the water tolerance wasfound to be 19%, aifurther 3.12 gms. KOH was. added when the water tolerance rose to 21%. (The water tolerance of the mixture without KOH addition was 10%.) The fluid thus produced had the following properties:

Water tolerance, 21%.

Freezing point, below -71 C.

Setting point, standard'method, '66 C. Acidity, 0.1 cc. TN/10 NaOI-I.

Example 3 300 cc. of 'theg'lyceryl tri-ricinoleate, as prepared in Example 2, had the'oil extracted by repeated washing with distilled water until no more soap could be extracted. The oil was finally dissolved in methyl ether and washed again. The 'ether and any water remaining in the oil was separated by distillation under reduced pressure. The product of this process was an oil somewhat lower in viscosity than the original glyceryl tri-ricinoleate. When mixed with Cellosolve in the proportion of 35% oil, 65% Cellosolve a water tolerance of 24% was'obtained without the addition of any potassium hydroxide. This regained oil was again heated to 0. under "reduced pressure and then filtered through silica gel.

When made up in 35% z 65% proportions a tfiuiircll dhaving the following properties was ob- Water tolerance, 24%.

Setting point (standard test), below 66 C. Freezingpo'int, 73 C.

Acidity, 0.6 .cc. N/10 NaOI-I on '20 cc. fluid.

The oil itself had the following characteristics:

Sap. value, 1128.8. Iodine value, 54.

As against the original glyceryl triericinoleatc which had Sap. value, 194. Iodine value, 57.19.

Example .4

The sodium alcoholate of .di-ethylene glycol, mono ethyl ether was prepared by reacting 23 gms. metallic sodium with 90 gms. of the monoethyl-ether. The dark brown solution obtained was added to a castor oil-'Cellosolve mixture in the proportions of 35% oil "to 65% Cellosolve and a water tolerance "of 25% was obtained immediately.

'I'claim:

1. A process for the production of a fluid for.

transmission of power which comprises mixin glyceryl tri-ricinoleate and a glycol mono-ether with a substance selected from the group con sisting of alkali hydroxides and alcoholates, the amount of said substance being in excess of that required to neutralise the free acidity of the triricinoleate, and when neutrality is reached separating the saponification products formed by washing with water and mixing the washed oil with further glycol mono-ether.

2. A process for the production of a fluid for transmission of power from glyceryl tri-ricinoleate and the mono-ethyl-ether of diethylene glycol in the proportion of about 35% tri-ricinoleate and about 65% glycol ether, which comprises dissolving an alkali hydroxide in a small portion of the glycol ether, the amount of alkali being in slight excess of that required to neutralise the free acidity of the tri-ricinoleate, and adding the resulting solution to the tri-ricinoleate and when neutrality is reached separating the saponification products formed by washing with water and mixing the washed oil with further diethylene glycol mono-ethyl-ether to bring the proportions to 35% oil 65% glycol ether.

3. A process for the production of a fluid for transmission of power from glyceryl tri-ricinoleate and the mono-ethyl-ether of diethylene glycol in the proportion of about 35% tri-ricinoleate and about 65% glycol ether, which comprises reacting an alkali metal with a small portion of the glycol ether, the amount of alkali being in slight excess of that required to neutralise the free acidity of the tri-ricinoleate, and adding the resulting solution to the tri-ricinoleate and when neutrality is reached separating the saponirlcation products formed by washing with water and mixing the washed oil with further diethylene glycol mono-ethyl-ether to bring the proportions to 35% oil: 65% glycol ether.

4. A process for the production of a fluid for the transmission of power which comprises mixing together about 35% glyceryl tri-ricinoleate and about 65% diethylene glycol mono-ethylether and adding an alkali metal to the mixture in excess of that required to neutralise with the alkali alcoholate formed the free acidity of the tri-ricinoleate, and when neutrality is reached separating the saponification products formed by washing with water and thereafter adjusting the proportions of the oil and glycol ether to 35% oil and glycol ether.

5. A process for the production of a i'luid for transmission of power which comprises contacting glyceryl tri-ricinoleate in the presence of the niono-ethyl-ether of diethylene glycol with excess of an alkali alcoholate over that required to neutralise the free acidity of the glyceryl triricinoleate, permitting the reaction to proceed until the free acid is substantially neutralised, and when neutrality is reached separating the saponification products by washing with water, and thereafter mixing the washed fluid with further glycol mono-ether.

6. A process for producing a power transmission fluid containing glyceryl tri-ricinoleate and mono-ethyhether of diethylene glycol, including the steps of mixing a small portion of the glycol employed with an excess of an alkali hydroxide over that required to neutralise the free acidity of the glycol tri-rincinoleate, adding the resulting solution to the tri-ricinoleate, permitting the reaction to proceed until the free acid of the triricinoleate is substantially neutralised, and when neutrality is reached separating the saponification products by washing with water, and thereafter adding the remainder of said glycol to the solution.

WILLIAM PERCIVAL SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,984,421 Muench et a1. Dec. 18, 1934 2,197,339 Gooding et al Apr. 16, 1940 2,205,183 Woodhouse June 18, 1940 2,238,045 Fulton Apr. 15, 1941 2,249,300 Weber July' 22, 1941 2,255,208 Fife Sept. 9, 1941 2,345,585 Clark et al Apr. 4, 1944 2,350,583 Bradley June 6, 1944 2,386,182 Balcar Oct. 9, 1945 FOREIGN PATENTS Number Country Date 348,642 Great Britain May 11, 1931 

1. A PROCESS FOR THE PRODUCTION OF A FLUID FOR TRANSMISSION OF POWER WHICH COMPRISES MIXING GLYCERYL TRI-RICINOLEATE AND A GLYCOL MONO-ETHER WITH A SUBSTANCE SLEECTED FROM THE GROUP CONSISTING OF ALKALI HYDROXIDES AND ALCOHOLATES, THE AMOUNT OF SAID SUBSTANCE BEING IN EXCESS OF THAT REQUIRED TO NEUTRALIZE THE FREE ACIDITY OF THE TRIRICINOLEATE, AND WHEN NEUTRALITY IS REACHED SEPARATING THE SAPONIFICATION PRODUCTS FORMED BY WASHING WITH WATER AND MIXING THE WASHED OIL WITH FURTHER GLYCOL MONO-ETHER. 